Патент USA US3031325код для вставки
April 24, 1962 I c. E. HENDEL ETAL 3,031,314 PREPARATION OF‘ DEHYDRATED POTATOES Filed March 16, 1960 S Sheets-Sheet 1 RAW POTATOE S In“ PEELING,TRIMMING, sLIcING,eI¢. 2” COOKING 34¢ MASHING i/ADDITIVES 4 PARTIAL DRYING . 54/ I GoND'ITIoNING I so ’ GRANULATING V 7” . DRYING \ PRODUCT F IG.I 0.5. HENDEL, G.K. NOTTER 9. RM. REEVE. INVENTORS BY A“ I m I April 24, 1962 c. E. HENDEL ETAL 3,031,314 PREPARATION OF DEHYDRATED POTATOES Filed March 16, 1960 _ 3 Sheets-Sheet 2 C.E. HENDEL, G.K.NOTTER Su R.M. REEVE. INVENTORS BY m April 24, 1962 3,031,314 C. E. HENDEL ETAL PREPARATION OF DEHYDRATED POTATOES Filed March 16, 1960 3 Sheets-Sheet 3 I000, 500- %\ % OVERcooKED 200' / AREA IOO coTsking,mafu’rle(o)thic : ‘<< OPTIMUM E 5O_ COOKING - AREA JNDER~ 20 - COOKE AREA |o_ D sl B 1 *’ I I80 I90 200 Temperature, °F. 2|0| 212 220 F I G. 6 37 VIBRATOR C.E. HENDEL,G.K. NOTTER 8| R.M. REEVE. INVENTORS 3,®3 1,3 14 Patented Apr. 24, 1952 2 v 3 3,031,314 ' PREPARATION OF DEHYDRATED POTATOES Carl E. Handel, George K. Nutter, and Roger M. Reeve, Berkeley, Caliti, assignors to the United States of America as represented by the Secretary of Agriculture Filed Mar. 16, 1960, Ser. No. 15,508 ' 4 Claims. (Cl. 9?--207) (Granted under Titie 35, US. Code (‘1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the less ‘sticky than those cooked by conventional methods. . As a consequence, subsequent procedures are simpli?ed. For example, the cooked potatoes can be granulated more readily. That is,- they can be readily subdivided into‘ ?ne particles without cell rupture. Also, potatoes cooked in accordance with the invention require less time of conditioning to put them in a granulable state as com pared with potatoes cooked by present methods. The cooking technique of the invention results in uni invention herein described, throughout the world for all 10 form cooking throughout the potato pieces with resulting , purposes of the United States Government, ‘with the uniformity of the dehydrated product eventually pro power to grant sublicenses for such purposes, is hereby duced. With conventional cooking methods, surface granted to the Government of’ the United States of layers tend to be over-cooked while inner portions tend America. be under-cooked. Such eli'ects leads to graininess of This invention relates to and has among its objects the 15 to some portions of the product and stickiness of other por provision of novel processes for preparing dehydrated tions when the product is reconstituted. potatoes. A particular obiect of the invention concerns The cooking process of the invention yields products the provision of improvements in the cooking, stage of which may be reconstituted with boiling water to pro the process whereby to facilitate subsequent steps and to duce mashed of a desirable mealy texture, free obtain products of new and improved properties. Fur 20 from pastinesspotatoes or graininess. ther objects and advantages or" the invention will be Moreover, the products of the invention may be ‘re evident from the following description taken in con constituted with water at room temperature. This method nection with the annexed drawing. Parts and percentages of reconstitution is of special advantage Where the dried set forth herein are by weight unless otherwise speci?ed. product is formed into mashed potatoes for freezing In the drawing, FIG. 1 is .a schematic ?owsheet illus trating procedures embodying the principles of the in vention. FIG. 2 is a view, partly in cross-section, of a granulator device useful for carrying out various steps in the process, including conditioning and drying as well as granulation. FIG. 3 is a cross-sectional end view taken on plane 3—3 of FIG. 2. FIG. 4 illustrates the granulator used in conjunction with a collecter for re ceiving dried product. vFIG. 5 illustrates another form of preservation, for example, in putting up frozen,v ready cooked dinners which merely require heating to make them ready for the table. In producing these ready cooked dinners, it is highly desirable to use room-tem perature water for reconstitution to eliminate need for cooling prior to freezing. Another point is that the products of the invention will absorb more water than productsmade with conventional cooking procedures. As a result, the products of the in apparatus for conditioning, granulating, drying, etc. FIG. 6 is a graph illustrating the temperature and time 35 vention will provide a greater amount of reconstituted mashed potatoes as compared with an equal weight of conditions in the cooking stage. conventional products. ' In the preparation of dehydrated potato products, it The objects of the invention are attained by cooking the is conventional to cook the raw potatoes at an early stage potatoes under controlled conditions. The conditions of in the process. For example, cooking is applied in pre paring all the dried products which are intended to be 40 cooking have been found to be critical and the improved results of the invention are attained by a correlation of table-ready on reconstitution of the dried product. No time and temperature. The inter-dependence of these table among such products are dried potato tlakes and dried potato granules. The latter terms are conven- . variables is best explained by reference to FIG. ,6 in the annexed drawing. In ‘this ?gure, the minimum and maxi tionally employed as designating dehydrated, pre-cooked mum cooking times corresponding to diiiere'nt cooking potatoes in ?ake and granular form, respectively. The cooking procedure presently employed in preparation of the various products is essentially the same as ordinary home-cooking methods. That is, the raw potatoes in the form of slabs or thick slices (about 3%" thick) are boiled in water until tender. Sometimes steam, instead, of boiling water, is applied to the potato pieces. In either case, the cooking is continued for about 20 to 30 min utes. The cooked potatoes while hot are then mashed and eventually dried in particulate form. Various spe temperatures are plotted with the temperature on a linear scale and the time on a logarithmic scale. Curve AB represents the minimum cooking conditions while curve CD represents the maximum cooking conditions. Thus, for example, if a cooking temperature of 180° F. is chosen, the potatoes are cooked from 75 to 420 minutes. ther conditions which may be used are, by Way of ex ample: At 190° F., 30' to 180 minutes; at 200° F., 12 to 45 minutes; at 212° F., 5 to 10 minutes. By operating cialized steps are employed depending on the, type of 55 Within the area ABDC, many signi?cant advantages are gained. Most important is that the potatoes are properly product to be produced. For example, in preparing dried potato granules by the widely-used “add-bacldlnethod, the mashed potatoes are mixed with su?lcient dried po tatoes from a previous batch to give a moisture content cooked yet the ?nal dried products are not sticky on re constitution. Moreover, operations subsequent to the cooking. step are simpli?ed and'take less time. For ex of about 32 to 35% for the composite material. This 60 ample, in the manufacture of granules, conditioning under identical conditions will require one-half or less time material is then ‘cooled and conditioned by holding it at about 60 to 80° F. for an ‘hour or more. ‘ The conditioned than potatoes cooked by conventional methods. Also, the potato material can be readily subdivided without cell composite material is then dehydrated in a pneumatic damage, thus to produce products free from stickiness on drier to produce the dried granules. Heretoiore it has not been recognized that the method 65 reconstitution. Other advantages have been mentioned of cooking has a profound effect on the properties of the above or are discussed ‘below in connection with operat ing outside of the preferred range. dehydrated product nor on the various procedural steps ' leading to the product. In accordance with the inven Our researches have shown that where the cooking is tion, the cooking is conducted under special conditions— carried out under conditions falling below curve AB, in described hereinafter—whereby many signi?cant advan 70 ferior results are attained. Under such condtions, there tages are obtained, including the following: Potatoes cooked in accordance-with the invention are are many uncooked particles and when the potato ma terial is treated in subsequent steps, so much mechanical 3,031,314 3 4 force must be applied to subdivide these particles that while at the same time removing moisture from it. That extensive cell rupture occurs. As a result, the ?nal dried is, the intensity of the mechanical forces are so con trolled as to achieve effective separation of one cell from another rather than rupture of individual cells. As a product on reconstitution forms a mass of undesirable pasty texture. Also, if the cooking is carried out under net result, the potato material is formed into ?ne parti conditions falling above curve CD inferior results are ob cles so that the end product will reconstitute rapidly and tained, these involving either (a) discoloration and de directly forming mashed potatoes free from lumpy or velopment of off-?avors, or (b) development of sticki gritty particles. Further, because cell rupture is kept at ness these respective defects depending on the tempera a minimum, the reconstituted product is free from pasti ture used. Thus, at the higher temperature ranges, about ZOO-212° F., cooking above curve CD leads to stickiness 10 ness. In preparing granules without add-back, this im proved method of subdivision is preferably applied after so that long conditioning times are required and subdivi the potatoes have been subjected to a series of steps sion without cell rupture is ditiicult to accomplish. At usually including cooking, mashing, and partial drying, lower temperature ranges, about 175—195° F., cooking above curve CD leads to discoloration (browning) and development of unnatural, undesirable ?avors. Generally it is preferred to carry out the cooking at a temperature of about 190° F. for the reason that at this temperature there is greater leeway than at higher tem peratures between minimum and maximum cooking times. Thereby the process can be more accurately con trolled and variations due to differences in composition of different batches of potatoes, localized or temporary temperature changes in the cooking medium, and the like, are canceled or at least minimized. Also, at the The subdivision step may be performed as a separate step or as part of other steps in the sequence of operations. Thus, for example, the potatoes may be cooked, mashed, partially dried, conditioned by known methods, sub divided in accordance with the invention, and ?nally dried. More preferably, the conditioning step is carried out while also applying the subdivision treatment. In this way the time of conditioning is substantially reduced and the potato material is more readily reduced to ?ne, non-coherent particles. Another preferred plan is to ap ply the subdivision treatment during the ?nal drying lower temperature range, 175-190” F., the thickness of the potato slices which are to be cooked is immaterial, stage as well as in an earlier stage. center of the piece or slice is undercooked while the sur cance of the subdivision. This has the bene ?t that the ?nal product is in especially ?ne particle size and exhibits a high density-very important in reducing and can be as much as one or two inches, or moderate packaging costs of the final product. It is evident from sized potatoes can even be cooked whole, Without ap the above that Where the subdivision step is applied in preciable non-uniformity of cooking through the ma terial. At higher cooking temperature it becomes more 30 conjunction with another treatment, for example, con ditioning or drying, it loses its identity as a separate, in important that slice thickness or piece size be small dividual step. This, of course, does not belie the signifi enough to avoid non-uniformity of cooking whereby the face is overcooked, with resultant loss of the bene?cial effects of the new cooking procedure. Thus at the high est cooking temperatures, about 205 to 212° F., it is preferred to use slices up to and including about one half inch, or other pieces with similar ratio of surface area to volume, for example, dice up to and including once inch on a side. The cooking, carried out under the conditions of time and temperature as explained above, is generally eifected by immersing the potato slices in a bath of water at the selected temperatures. Another plan is to subject the potato slices to a current of steam or other hot gases. For cooking at temperatures below 212° F., mixtures of steam and air proportioned to provide the selected tem perature, are useful. It is to be noted that in the method of the present in vention, the raw potatoes are given a single cook at pre scribed conditions of time and temperature. This proce dure is in contrast with methods which have been previ ously advocated wherein the potatoes are given a pre cook at relatively low temperatures followed by a cook at boiling temperatures. The potatoes, cooked in accordance with the invention, may be subsequently treated by any of various processes which lead to the production of dried potatoes in particu late form. Regardless of the type of product eventually produced, the advantages outlined above will be realized. As examples, the cooked potatoes are mashed and then treated by known procedures to produce dried ?akes or For a complete understanding of how the principles of the invention are applied in practice, the following de tailed description is provided: Referring to FIG. 1 in the annexed drawing, in stage 1 the raw potatoes are subjected to the usual preliminary steps of washing, peeling, trimming, and slicing. The 40 tubers are cut into slices which may range about from one-eighth to one inch in thickness. To preserve ?avor and color, it is preferred to dip the slices in a sulphite solution prior to further treatment. Usually an aqueous solution containing about from 0.5 to 1.25% of sodium r sulphite or bisulphite is used and the slices dipped there in for a few minutes. For example, slices a quarter inch thick are dipped one minute in a 0.5% sulphite solution while slices three-fourths inch thick are dipped ?ve minutes in a 1.25% sulphite solution. Usually the con ditions of dipping are adjusted so that the slices contain 50 about from 200 to 500 parts per million (p.p.m.) of S02 on a dry basis. Sulphiting may be applied at this stage as just described, but as an alternative it may be applied at a later stage, for example, after cooking and mashing. Another alternative is to apply part of the sulphite as described above and a further amount after cooking and mashing. Another alternative is to apply all or part of the sulphite by adding sulphur dioxide to the air or other gaseous medium applied to the potatoes during such steps as conditioning, granulating, drying, etc. Also, all or part of the sulphite may be applied in the soaking step de scribed below. Techniques for converting mashed potatoes An advantageous procedure which may be applied to into such products are well known in the art and any of the raw potato slices is to soak them in water to increase their moisture content. This has the desirable effect that granules. the procedures may be employed. Techniques for pro ducing granules are disclosed, for example, by Neel et a1., Food Technology, vol. VIII, pp. 230-234, 1954, and processes of producing ?akes by Willard et al., U.S. Patent 2,780,552. the dehydrated products produced therefrom display an abiilty to absorb more water on reconstitution than otherwise would be the case. The procedure employed simply involves soaking the raw slices in water until their weight increases about 10% by absorption of Water. De A preferred technique of converting the potatoes, pending on such factors as piece size, variety of potato, cooked in accordance with the invention, into dried etc., the soaking to attain this effect may require any granules without necessity for “add-back” is disclosed be where from one to four hours. The soaking step if low. A principal feature in this procedure is that sub employed is a useful point at which to impregnate the division is accomplished by subjecting the potato ma terial to repeated mild compression and mild shear forces 75 potato tissue with sulphite. Hence, the water may con ‘5 3,031,314 tain a small proportion, say 0.02 to 0.1% of sodium sulphite or bisulphite. This sulphiting procedure may be used instead of, or in conjunction with, sulphiting at other stages in the process. In stage 2, the potato slices are cooked under controlled conditions of time and temperature as described above. In stage 3, the cooked potatoes—while hot-are mashed in conventional manner. This operation may be carried out by pressing the cooked potatoes between warm rolls, by pressing them through a screen, or by other conven 5 simultaneously contacting it with a stream of air. Under ‘these conditions, and especially when the potatoes are cooked in the special way described above, the condition ing above freezing temperatures is completed in a maxi mum of three hours and in many cases in one to two hours. More frequent mixing or ?u?ing is required When the mash is being cooled than at other times during the conditioning, because the hardening of the mass is ac celerated by the evaporation of moisture from the product during cooling. The mixing or ?uf?ng is a form of the mild compressive-mild shear action. It is important that tional potato-mashing techniques. During or after mash ing, various additives may be incorporated into the mash. the compressive portion of the forces be especially mild Thus, to preserve color and ?avor, a minor proportion in the early stages of conditioning. Otherwise, the ma~ of sodium sulphite or bisulphite may be added, Gener terial, which is somewhat cohesive in these early stages, ally, enough sulphite is added to provide about 200 to 15 will be agglomerated by the action, rather than separated, ‘500 ppm. of S02 on a dry basis, including that incor and longer time will be required for the material to be porated in the previous sulphite dipping step or other sul come friable. phiting operation, where such are used. Minor propor In stage 6, ‘the conditioned material is granulated and tions of fat-stabilizing antioxidants such as nordihydro dried through the critical moisture range. The granula guairetic acid, butylated hydroxy anisole, butylated hy droxy toluene, etc., may be added to prevent rancidi?ca tion of the natural fat in the product on storage. To in crease ability of the product to absorb moisture and to reduce stickiness, edible dispersing agents such as the 20 tion and drying are carried out either simultaneously or in closely successive operations repeated a number of times. (Where conditioning is carried out at subfreezing temperature, the mash is thawed before granulating.) In this granulating step the aim is to subdivide the mash into monoglyceryl esters of long-chain fatty acidsmay be in 25 particles containing not more than about ten individual corporated in the mash. Other substances which may be cells, preferably unicellular particles, and it must be done added are such food ingredients as salt, whole milk solids, by separating one cell from one another rather than by non-fat milk solids, etc. rupturing individual cells. Were the latter to be done the In stage 4, the mashed potatoes are partially dehydrated. product would yield a pasty, unpalatable mass on recon This may be conveniently done with a double-drum drier. stitution, 'Ihe granulation can be successfully accom The mashed potatoes are fed into the nip between rotating, plished by applying to the mass repeated mild compression heated drums and the partially dried potato material is and mild shear forces. Preferred methods by which this removed by scraper blades. The drier drums are gener end can be attained are explained below in connection ally heated to a temperature in the range about from 150 with FIGS. 2, 3, and 5.‘ Any coarse potato material pre to 300° F. The temperature of the drums, the speed of 35 sent after granulation may be recycled back to the condi rotation, and the thickness of the ?lm of potato material tioning step (stage 5). are so correlated that the partially dried potato mash has In stage 7, the granulated potato material is further de a moisture content about from 50 to 75%, preferably hydrated to produce the dried granules. This ?nal de about 60%. Although partial drying on heated drums is hydration may be carried out in any manner as is con a preferred technique, it is notessential to use it. Thus 40 ventional in the art. As an example, the potato material other conventional dehydration procedures such as expos may be dehydrated by procedures incorporating the prin ing thin layers or extruded portions of the mash to a cur ciple of ?uidization. To this end, the potato material is rent of hot air, vacuum dehydration techniques, and so placed in a vessel provided with means for jetting minute forth, can be employed. streams of hot air up through the bed of material tending Following partial drying, the potato material in stage 5 45 to keep it in a ?uidized state while being dried. Apparatus is subjected to cooling and conditioning to eliminate its of this type and method of employing it to dehydrate doughy texture and make it friable. In this stage the moist potato particles are disclosed by Neel et al. (Food temperature of the mash is reduced to temperatures rang Technology, 1954, vol. VIII, pp. 230-234.) To further ing from about 100° F. down to subfreezing tem eratures. promote ?uidization of the product in the early part of 50 The conditioning may be effected in various ways. For this drying operation, this ?uidized-bed drier can be sub— example, the potato material may be held without mixing jected to continuous vibration or shaking, or a mechanical in closed containers in the presence of adventitious air agitator can be employed. In the alternative, the granu or in the absence of air, that is, under vacuum or in an lated potato material may be dehydrated in pneumatic~ atmosphere of an inert gas such as nitrogen. Where the type drielis, for instance, a device of the type disclosed conditioning is at temperatures above freezing, the mash 55 by ()lsonlet al. in Food Technology, vol. VII, pp. 177 may be subjected to occasional or periodic ?u?ing or mix 181 (1953).’ This device consists essentially of a long, ing during conditioning to minimize formation of aggre vertically positioned duct. Hot air at about 2l2-392° gated masses vthat would subsequently be di?icult to sep F. is forced upwardly at high velocity (i.e., about 1000 arate without rupture of cells. Thus, for instance, ‘the ft./min.) through the duct and the friable granulated po potato mash may be‘ carried on an elongated conveyor 60 tato material is fed into this air stream. As the current belt while it is subjected to the action of rotating paddles of air carries the material upward it is dehydrated. At or similar devices which exert a gentle mixing or ?u?ing the top of the duct is a conically diverging diffuser so action to effect separation of the mass Without rupture that as the current rises into the diffuser its velocity is of individual cells. During the conditioning, the mash gradually diminished. A deflector is positioned above the may be contacted with a current of air or an inert gas 65 diffuser whereby the now slowly moving current is de such as nitrogen to cool the product to temperatures from ?ected downward causing the dried potato granules to about 100° F. down to about 30° P. if conditioning is drop out of the air stream so that they can easily be sep above freezing, or to freeze the product if conditioning arated from‘the moist exhaust air. In a preferred method, is brought ‘about by freezing. A minor proportion of sulphur dioxide may be added to 'the gas stream, particu larly in the event that in previous steps the usual amount of sul?te is not added to the mash. In the preferred the ?nal dehydration is accomplished while the potato material is subjected to repeated mild compression and mild shear forces, as described below in connection with FIG. 4. ‘In any event, after ?nal drying the product has modi?cation the conditioning is carried out by applying a moisture content of about 5 to 8%, preferably ‘about to the mash occasional or periodicimixing or ?uf?ng while 75 6%. 3,031,314 Reference is now made to FIGS. 2 and 3 which illus trate one modi?cation of apparatus for effecting the gran ulation and drying through the critical moisture zone. The apparatus, generally designated at 20, comprises a trough or U-shaped chamber 22 provided with a remov able lid 23 and a longitudinal shaft 24. Suitable equip ment, not illustrated, is provided to rotate shaft 24 in the direction shown at a low speed—-about 1 to 5 r.p.m. Attached to shaft 24 are a series of arms 25, each bearing a paddle 26. Dimensions are so chosen that the tips of paddles 26 have a clearance on the order of one-fourth to one-half inch from the cylindrical base of trough 22. Also positioned on shaft 24 are arms 27 which carry a the potato material is so horny that it cannot be sub divided without cell rupture. However, where the gran ulation is conducted while repeatedly applying the mild compression and mild shear forces and simultaneously contacting the mash with a draft of drying gas, this treat ment being continued while the moisture content of the mash passes through the range from about 50% moisture down to about 35% moisture, the potato material is effectively granulated without cell rupture and the gran ulated product displays a minimum tendency to cohere in subsequent operations. In operating under this sys tern, it is evident that there is at least a partial merging of stages 6 and 7 because in both of these stages there is granulation as well as drying. The apparatus illustrated in FIGS. 2 and 3 can be em 22. Blade 28 is made of ?exible material such as silicone 15 ployed for drying the granulated potato material. In rubber (Silastic), neoprene, Te?on or other elastomer deed, this is a preferred method as it permits reducing and is so positioned that its edge actually wipes against the moisture content through the critical zone mentioned the cylindrical base of trough ‘22. This base may be pro blade 28 which extends essentially the length of trough above while simultaneously subjecting it to granulation vided with small protuberances, as by welding wires lon gitudinally along it, to increase the shearing effect to the 20 with mild compression and mild shear forces. To this end the granulator 20 is connected to a product-collection desired level. An inlet conduit 29 is provided for intro system as shown in FIG. 4. Referring to this ?gure, the duction of gaseous media, for example, air for drying. exit conduit 3t) is connected to collector 21. In opera In using the illustrated device to granulate the potato tion, the dried product is carried by the current of air material, conditioned potato mash-produced as above described-is introduced into trough 22. Shaft 24 is then 25 out of trough 22 into collector 21, the product dropping through discharge port 31 and excess drying air being caused to rotate and drying air is introduced through released through vent 32. In drying in this way, the inlet conduit 29. The resulting action of paddles 26 and ‘amount and temperature of the air introduced into the blade 28 effect the granulation of the potato material. Thus, paddles 26 cause a repeated mixing of the material 30 system via conduit 29 are increased above the levels used in the preceding stage. Thus, for example, the air tem and a ‘disintegration of the larger aggregates of cells. perature used is about from 150 to 250° F. The velocity Blade 28 being actually in contact with the cylindrical base of trough 22 effects a further size reduction of the of the air is increased so that the current is strong enough very readily separated from one another. This is at the rial may ‘be introduced into trough 22 and shaft 24 started to rotate, this being continued throughout the process. At ?rst, air at about room temperature is intro duced into the system through conduit 29. Then as the to carry out from trough 22 the ?ne dry particles. Dur particles. The reduction in particle size effected by the device is essentially limited to separation of individual 35 ing the drying cycle, shaft 24 is rotated, as during the granulation, to maintain the potato material in a loose cells one from another as contrasted with rupture of in and bulky state and subdivide any larger particles found dividual cells. Important in this regard is the fact that by re-aggregation of ?ner ones. During operation, the paddles 26 and blade 28 exert what may best be termed particles discharged from pipe 31 are examined and the as mild compression and mild shear forces. Thus the mechanical forces exerted by these elements are of suffi 4-0 velocity of the air stream adjusted so that essentially only the properly-dried, ?ne particles are carried by the air cient intensity to separate agglomerated cells but insu?i stream into the collector and the aggregated particles cient to rupture individual cells. The action is continued remain in chamber 22 for further drying and subdividing. until the potato material forms a well-granulated mass It is further evident that granulation and drying need of unicellular particles and small aggregates of unicellu not necessarily be carried out as separate and distinct lar particles that have only a very slight tendency to steps. Thus, for example, the conditioned potato mate agglomerate together. Any agglomerates formed are lower end of the critical moisture region where the potato material contains about 32 to 45% water, the pre cise moisture value depending somewhat on the previous history of the material. During the granulation, the potato material is contacted with a current of air, for example, at a temperature about from 75 to 200° F., to cause the desired reduction in moisture content during granulation. Ordinarily, the product remains at room temperature (about 75° F.) during the granulation. The warm air introduced does not appreciably raise the tem operation continues the air temperature is gradually in creased up to suitable temperatures for drying. Like wise, during the later stage of the process, the velocity of the air stream is likewise increased to entrain the dried ?ne particles and carry them out of the trough. Moreover, the trough granulator may be used for all three stages—conditioning, granulation, and drying. perature of the potato material because of the cooling Thus, for example, the partially-dried hot mash is intro potato material, as regards granulation, and its moisture cooling may be applied as by contacting the mash with duced into trough 22 and shaft 24 rotated either contin effect as water is evaporated therefrom. Moreover, our researches have shown that there is an 60 uously or at intervals until the mash loses its doughy texture and becomes more friable. During conditioning, important relationship between the properties of the content. Knowledge of this relationship permits us to air at room temperature or below. After the potato obtain signi?cant advantages in the production of potato material begins to lose its doughy texture, the shaft is critical moisture range. Thus, our researches have indi tually, the velocity of the air stream is increased to en train the ?ne dry particles and carry them out of the trough into the collector system. In FIG. 5 is illustrated an alternative form of apparatus granules. It has been found that the granulation is most 65 rotated continuously, this being continued throughout the process, while the air temperature is gradually in effectively accomplished while the moisture content of creased up to suitable temperatures for drying. Thereby the potato material is reduced from about 50% down to the product is subjected to granulation and drying. Even about 35%, this range being herein designated as the cated that if the granulation is applied only at higher moisture levels (that is, above about 50%) the product retains so much cohesiveness that the particles will re which may advantageously be utilized in the conditioning, aggregate when subjected to subsequent operations. On granulating and drying steps. This apparatus includes a the other hand, if the granulation is not effected until the moisture content of the mash is reduced to below 35%, 75 rectangular frame 35, supporting a screen 36. This screen 9% 3,031,314 is of v?ne mesh construction (80- to lSO-mesh, for in~ stance) to allow air 1to ?ow-through but to prevent the potato material from passing through it. Frame 35 is connected to vibrator 37, of conventional construction, to vibrate the device. 'Journaled on frame 35 are a series In the examples, products were tested for blue value index by the method of Mullins et al. (Food Technology, vol. 9, p. 393) on a basis of 21/: grams of dry solids. This determination furnishes a measure of release of free starch from'the cells and a higher value denotes more free starch. of shafts 38 rotated in the direction shown by suitable equipment at moderate speed (about 50 to 150 r.p.m.).» In another test, moisture absorption of the products was whereas the soft, ?exible, elastic blades 28 actually con mashed potatoes are formed from a standard amount of measured by a modi?cation ‘of the method of Potter Secured to shafts 38 are arms 25 and 27, hearing paddles \(Iour. Ag. and Food Chem., vol. 2, p. 516; 1954). This 26 and blades 28, as described in the modi?cation of FIGS. test determines the volume of reconstituted mashed po 2 and 3. As in that modi?cation, paddles 26 clear screen 10 tatoes formed per unit weight of dried granules. In this 36 by a distance of about one-eighth to one-fourth inch case a higher value indicates a superior product as more tact ‘the screen. In using the device the potato material dry material. is placed on the screen 36 at the upper (right-hand) end Example I and shafts 38 are rotated while ‘the frame is vibrated. In 15 Idaho Russet Burbank potatoes were washed, peeled, small-scale construction the material arriving at the lower trimmed, and cut in three-fourths inch thick slices. end of the screen may be collected and replaced at the The‘slices were dipped five minutes in a 1.25% aqueous higher end for continued action. On a larger scale the solution of sodium bisulphite. The slices were then dimensions and the number of shafts and associated mech cooked 60 minutes in a mixture of air and steam having anisms are selected to properly treat the material in a a temperature of 190° F. single pass. The device, as that‘of FIGS. 2 and 3, may The cooked potatoes were mashed by pressing through be employed in any of the stages of conditioning, granu a one-half inch mesh screen, then blended in a planetary lating, dr-ying, or any combination of them. Air for de type mixer for one minute with 10% of their Weight of creasing the moisture content of the potato material dur ing treatment is forced upwardly through duct 39‘, con 25 water containing 0.6 gram of sodium bisulphite per ten pounds of potatoes. nected to frame 35 via ?exible coupling 40. Where the The potato mash was then partially dried on a single system is used for producing a dry product, a hood and drum drier-drum temperature 250° F., speed of drum collector of conventional design may be positioned above 2.5 r.p.m.‘ The partially-dried mash had a moisture con frame 35 for collecting the dried product. _ As has been noted brie?y above, the present invention 30 tent of 56.5%. The partially-dried mash was then conditioned. To may advantageously be applied in the manufacture of po this end, it was placed in a trough granulator as depicted tato granules by the add-back process whereby to obtain in FIGS. 2 and 3. The shaft was rotated (2 r.p.m.) con signi?cant advantages including (1) elimination or at tinuously during addition of the mash (30 minutes), then least marked reduction in time of conditioning, (2) reduc for the next hour the shaft was rotated ?ve minutes out tion in amount of “seed” which needs to be recycled and (3) reduction in stickiness of the ?nal product on re of each 15-minute period. During this operation the tem constitution. Thus advantages result from the fact that with the new cooking procedure there is (1) substantially improved granulability of partially dried potatoes, and (2) much improvement in texture of the ?nal product. 40 perature of the mash decreased from about 125° F. to about 65° F. The mash was then friable and ready for the beginningof granulation. It was near the upper limit of the critical moisture region referred to above. To granulate the conditioned mash, it was left in the In applying the invention to the add-back process, potatoes trough granulator and the shaft was operated continuously are subjected to the preliminary steps (stage 1) and to the (2 r.p.m.) for one hour while air at room temperature new cooking procedure (stage 2) as described above. was blown through the device. Moisture content of the The cooked potatoes are then mashed and mixed with su?lcient “seed” granules‘ (that is, dried granules from a 45 material was reduced to 50.5%. The material was near the middle of its critical moisture region. It was now previous batch) to form a composite having a moisture granulated well enough that the rate of drying could be content of about 32 to 35%. This composite material is increased without resulting in an excessive proportion of then cooled to about room temperature, preferably while coarse dried product. applying‘repeated'mild compression and mild shear forces The potato material-—still in the trough granulator and as described above, using the granulator device of FIGS. 50 with the collector attached as in FIG. 4——was subjected 2 and 3 or that of FIG. 5. The material can then be to a current of air at 200° while the speed of the shaft dried directly-—no conditioning step is required as in was increased to 5 r.p.m. yIn about 30 minutes, 94% of previous practice. Thus in conventional practice the the dried granules were received in the collector. This composite (freshly mashed potatoes plus seed granules) must be conditioned at room temperature for at least an 55 product containing 20% moisture was then ?nish-dried in a ?uidized bed drier to produce granules of 6% moisture hour. In an alternative method, the present invention content. The product had a blue value index of 17, in maybe used in the manufacture of potato granules by the dicative of very slight cell damage. Bulk density of the add-back process to obtain a product of very ?ne texture product was 0.92 gram/cc; moisture absorption was 5.7 (unusually low blue value), again without conditioning of the material before drying. (Elimination of the condi 60 cc. of reconstituted mash per gram of product. A portion otthe product on reconstitution‘with boiling water formed tioning period .is important as there is .then much less op mashed potatoes of a desirable mealy texture free from portunity for 'quality changes, by oxidation or other de both pastiness and graininess. teriorative reactions.) [In applying this process the po tatoes are treated as above described-preliminary steps (stage 1), special cooking (stage'2), mashing (stage 3‘), and partial-drying (stage 4), then mixed with su?icient Example II 65 A quantity of Idaho Russet Burbank potatoes was washed-peeled, trimmed,>sliced, and given a 5-minute dip “seed” granules to give a moisture content of 30 to 40% in 1.25 % aqueous sodium bisulphite solution. The ma for composite material. The composite material is mixed terial was then divided into several lots which were and cooled to room temperature, preferably while apply ing repeated mild compression and mild shear forces as 70 cooked under ditferent time and temperature conditions set forth below. For comparison, several lots were described above, using the granulator device of FIGS. 2 cooked under conditions outside ‘the scope of the inven and 3 or that of ‘FIG. 5. The fl'fl'?lel'ldl'iS them directly tion; these included lots A1, A4, A5, and Cl. dried-no conditioning period is ‘needed. . Following cooking, each lot was converted into granules ‘The invention is further demonstrated ‘by vthe following by the ‘same method. This method involved these steps: illustrative examples. 75 The cooked potatoes were mashed by pressing through 3,031,314 12 The slices were dipped ?ve minutes in a 1.25 % aqueous solution of sodium bisulphite. The slices were then cooked for 90 minutes in a mixture of steam and air having a temperature of 185° F. The cooked slices were mashed and mixed with 10% of their weight of water containing 0.6 g. of sodium bisul a one-half inch mesh screen, then blended in a planetary type mixer for one minute with 10% of their weight of water containing 0.6 gram of sodium bisulphite solution per ten pounds of potatoes. The potato mash was then partially dried on a single drum drier—drum temperature 250° F., speed of drum phite per ten pounds potatoes and with seed granules using six pounds seed to three pounds cooked potatoes. (In the ?rst run, the seed was commercial potato granules; 3.5 r.p.m. The partially-dried mash had a moisture con tent of about 55%. The partially-dried mash was then conditioned. To this end, it was placed in a trough granulator as depicted 10 in subsequent runs, the seed was granules from the next previous run.) The mixing was done in a planetary-type in FIGS. 2 and 3. The shaft was rotated (2 r.p.m.) con food mixer and in ten minutes the temperature of the tinuously during addition of the mash (30 minutes) then mix was about 110° F. Air was blown into the mixer the shaft was rotated ?ve minutes out of each 20-minute for ?ve minutes longer, at which time the mix was cooled period. In about 90 minutes the temperature of the mash decreased from about 125° F. to about 65° F. The 15 to about 75—80° F. Mixing was then discontinued. The cooled composite was then dried in a pneumatic conditioning was continued until the potato material (air-lift) drier using a current of air at 260° F. lost its doughy texture and became friable. The time re The dried material was screened through an 8-mesh quired for this result varied with the diiferent lots as screen, the coarse material retained on the screen being indicated in the table below. To granulate the conditioned mash, it was left in the 20 weighed and discarded as “scalping loss.” The ?ne ma terial was then put through a 60-mesh screen, the ma terial on this screen being reserved as seed for the next trough granulator and the shaft was operated continu ously for one hour while air at room temperature was blown through the device. Moisture content of the ma terial was reduced to about 50%. cycle, the material passing through the screen being the granule product. The process as described above was repeated some 15 The potato material-still in the trough granulator and 25 times, each representing a cycle. It may be noted that it requires about ten cycles to produce representative re sults, that is, elimination of. the effect of the seed originally used. with the collector attached as in FIG. 4-was subjected to a current of air at 200° F. while the speed of the shaft was increased to 5 r.p.m. The product received ‘in the collector, containing about 20% moisture, was ?nish-dried For control purposes, the same procedure was applied in a ?uidized bed drier to produce granules of about 6% 30 except that the cooking conditions were conventional. moisture content. Thus the potato slices, in this case three-fourths inch The conditions used and the results obtained are tabu thick, were cooked in steam (212° F.) for 25 minutes. lated below: Condi- Lot A—1____ Size of raw potatoes, Inches 1% x )4 x %____ 212 (steam) __________ ._ A—2__-_ ,1/2 x V2 x 96 _______ __d A—3__-_ % x )1; x 12 _______ __do__-__ A-4___- % x % x )5 _______ __do-____ Blue Texture on Texture on Cooking tioning value reconstitution reconstitution time, time index of with water with water Min. required, granules at 170° F. at 212° F. Hrs. Cooking temp, ‘’ F. 5 104 7 9 3 3 49 Good ______ __ Pasty. Excellent.__. Excellent. Do. l5 4 A-5____ % x % x % _______ __do _______________ __ 25 4 B .... _. % (slices)___-_ .200 (steam and air). 20 2. 5 Excellent. 7 2 2 Pasty. Excellent. D0. C-l. ___ % (slices)_C—2____ __.__do___ 190 (steam and air) __.do__ ___ 3 _ 25 60 150 Pasty. Do. The results obtained are tabulated below: Example III A Raw potatoes were cut into free-fourths inch slices and cooked in a steam-air mixture at 190° F. for various times 50 as described below. Each batch of cooked potatoes was then separately dried using the following technique. The B With New Cooking With Regular Cook Method 185° F., 90 Min. 212° F., 25 Min. Cycle Number cooked potatoes were mashed, frozen and while frozen Blue Scalping Blue Scalping Value of Loss, Value of Loss, Product Percent Product Percent extruded through rolls spaced apart 0.01 inch to produce platelets having essentially monocellular thickness. This 55 product was put on trays and dried in a current of air at 120° F. Seed (Commercial granules)" ___ The various dried products were then subjected to certain tests. In one test, the products were reconstituted with boiling water, 90 cc. per 20 g. product, and the re sulting mashed potatoes were rated for texture, color and ?avor by a panel of skilled food tasters. 78 70 ________ __ 24 65 G4 64 62 59 31 13 9 7 6 59 14 59 9 78 76 ________ __ 7 89 89 92 117 124 7 14 24 34 36 .................. __ __________________ _ The results are tabulated below: The steady improvement in blue value and scalpmg Cooking Time, Properties of Reconstituted Product 65 loss in run A (with the new cooking method) as con trasted with the steady deterioration of quality in run B (regular cooking) demonstrates the improvement ob tained with the new cooking method. m. Contained uncooked lumps; typical ?avor and color. No uncooked lumps; typical ?avor and color. o. No uncooked lumps; brownish discoloration and off-?avor. Example IV 70 Example V Idaho Russet Burbank potatoes were washed, peeled, trimmed and cut into three-fourth inch slices. The slices were dipped ?ve minutes in a 1.25% so dium bisulphite solution. The slices were then cooked Idaho Russet Burbank potatoes were washed, peeled 75 for 60 minutes in water at 190° F. and cut into one-half inch slices. 3,031,314 13 14 The cooked slices were mashed and blended with 10% of their weight of water containing 0.6 g. of sodium bi sulphite per ten pounds of potatoes. The mash was par tially dehydrated on a double-drum drier~drum tem perature 200° F., speed of drums 1 r.p.-m., clearance be tween drurns 0.015". The partially dried mash had a and subjecting them to dehydrating conditions to produce dehydrated potatoes. 2. The method of preparing dehydrated potatoes which comprises subjecting raw potato slices to a single cooking operation at a temperature of about 190° F. for about 60 minutes, directly mashing the cooked potatoes and sub jecting them to dehydrating conditions to produce dehy moisture content of 75%. The partially dried mash was then mixed with seed drated potatoes. 3. The method of preparing dehydrated potatoes which for the ?rst cycle and material from a previous run for 10 comprises subjecting raw potato slices to a single cooking granules (3# mash, 4# seed) using commercial granules the next succeeding cycles. The mixing was in a plane operation ‘at a temperature of about 190° F. for a period tary-type ‘food mixer for 15 minutes. The material was of about 60 minutes, directly mashing the hot cooked then dried on the vibrating screen drier shown in FIG. 5 potatoes, subdividing the mash into particles and dehy with parts 27, 28 removed. Air at 190° F. was blown up drating it to produce dehydrated potatoes in particulate through screen 316. The product was dried to about 1Q.% 15 form. moisture content. 4. The method of preparing dehydrated potatoes which The dried ‘granules were then put through Semesh and com-prises subjecting raw potato slices to a single cooking 60-mesh screens as described in Example IV. operation at a ‘temperature of about 190° F. for about The results are tabulated below: 60 minutes, directly mashing the cooked potatoes, suc 20 cessively subjecting the mash ‘to partial drying, condition ing, granulating, and ?nal drying to produce dehydrated potatoes in dry granule form. Blue Value of Cycle Number Granules feed s--. (Commercial ‘‘‘ " granules) _________________________ ' ____ __ ._ References Cited in the ?le of this patent 55 25 8 _____ __ . ._ 10 12 39 _ ___ UNITED STATES PATENTS 40 31 2,780,552 2,787,553 Willard _______________ __ Feb. 5, 1957 Oording ______________ __ Apr. 2, 1957 Having thus described the invention, what is claimed is: OTHER REFERENCES 1'. The method of preparing dehydrated potatoes which 30 comprises subjecting raw potato slices to a single cooking Talburt and Smith: 1959, “Potato Processing,” pp. operation at temperature and time conditions within the 309-310. area ABDC in FIG. 6, mashing the potatoes while hot Talburt: “\P‘otato Processing,” 1959, pp. 330-331.